Connectors have widely been used for conveniently connecting and disconnecting a large number of signal lines. Among many connectors, insulation displacement connectors are known for making electrical connection between the conductor of an insulated electrical wire and a contact by simply forcing the insulated electrical wire into such contact, to break the insulator, thereby eliminating the need for stripping the insulator at the end of the insulated electrical wire in order to solder or crimp the conductor to the contact.
Illustrated in FIG. 4 is an exploded perspective view of one example of one such conventional insulation displacement connector 100. A large number of contacts 10 are inserted in a large number of grooves 21 provided in a housing 20 at a predetermined pitch. Although not shown in FIG. 4, the grooves 21 are also provided in the lower side of the housing 20 to receive contacts 10 from below. The contacts 10 are provided with mating sections 11 at their front portions for making electrical contact with contacts of another matable connector (not shown) and insulation displacement connection (IDC) sections 12 at their rear portions for receiving sections 1a of the insulated electrical wires 1 (see FIG. 1) for electrically engaging conductors 2 of the insulated electrical wires 1.
On pushing the insulated electrical wires 1 into V-grooves 12a of the IDC sections 12, the insulation layers 3 are severed for making electrical contact with conductor 2. Sections 1b of electrical wires 1 are pushed into wire retention grooves 22 in housing 20 simultaneously with the insertion of end sections 1a into IDC sections 12 of the contacts 10, thereby securing the insulated electrical wires 1 in connector 100.
The housing 20 including the insulated electrical wires 1 connected to the contacts 10 in the manner described above is coupled to another housing 30. The assembly is then sandwiched between upper and lower covers 40 (only lower cover is shown in FIG. 4) before being covered with a metal cover 50 from the front end to complete the insulation displacement connector 100.
Illustrated in FIG. 5 is a front view of the electrical wire retention grooves 22 of housing 20 for the insulation displacement connector 100 of FIG. 4 as seen from the ends of electrical wires 1.
There are formed projections 23 in each electrical wire retention groove 22 adjacent to its entrance in such a manner as to limit the width of the entrance smaller than the diameter of the electrical wire 1. The electrical wires 1 are forced into the respective grooves 22 through the narrower entrance and are retained in the grooves 22 by downwardly facing shoulders 23a of projections 23.
Illustrated in FIG. 6 is a simplified view of electrical wire 1 just before being inserted into the IDC section 12 of the contact and in the wire retention groove 22 in housing 20. The electrical wire 1 is placed over the IDC section 12 and the wire retention groove 22 and is then inserted into the IDC section 12 and the electrical wire retention groove 22 by tool 60. The insertion tool 60 has grooves 61, 62 at positions corresponding to the IDC section 12 and the electrical wire retention groove 22 so that the electrical wire 1 is pushed down at both sides of both the IDC section 12 and the electrical wire retention groove 22.
As described hereinbefore, the electrical wires 1 are inserted and held in the electrical wire retention grooves 22. However, the grooves 22 are forced to widen their entrances by the electrical wires 1 hitting the projections (see FIG. 5) when the electrical wires 1 are being inserted in the electrical wire retention groove 22 by the insertion tool 60. This tends to deform the housing 20 downwardly at and near its center portion of the back end portion (lower right portion in FIG. 4) as shown by an arrow A.
If such deformation occurs, not only the electrical wire retention grooves 22 but also the contacts 10 tend to move in the direction as shown by an arrow B in FIG. 6. There may be an instance that the IDC sections 12 move beyond the groove 61 in the insertion tool 60 as shown by the dashed line C. If the insertion tool 60 is operated to push down the electrical wires 1 under this condition, the IDC sections 12 are crushed by the insertion tool 60 and no proper electrical connections can be made between corresponding conductors 2 of the electrical wires 1 and the contacts 10.
Also, widening the electrical wire retention grooves 22 may cause misalignment between the pitch of the electrical wires 1 and the IDC sections 12 of the contacts 10 disposed in the housing 20. This may result in the electrical wires 1 riding over the blades 12b of the IDC sections 12 of the contacts 10 (see FIG. 4) and cutting the conductors 2 by blades 12b when the electrical wires 1 are pushed down.
Illustrated in FIG. 7 is a cross section view of another conventional electrical wire retention grooves 22'.
The provision of projections 24 extending downwardly at a certain slope as illustrated in FIG. 7 rather than the simple projections 23 in FIG. 5 may be effective to solve the above problem because the deformation of such projections 24 during insertion of the electrical wires in the grooves 22, absorbs the force which would otherwise widen grooves 22'.
However, in order to enjoy the effectiveness of such downward projections 24, such projections must have a proper length thereby requiring higher raised portions 26 to form the electrical wire retention grooves 22' and making the insulation displacement connector bulky. There are increasing needs for compact connectors having a large number of signal carrying contacts at a small pitch therebetween. In this case, the width of each raised portions 26 must be small and forming such slanted downward projections is increasingly difficult.
In light of the above problems, it is proposed to provide the present device which is intended to provide an electrical connector free from such deformation and suitable for miniaturization.